This invention relates to an improved sodium aluminum phosphate for baking applications, and more particularly to a potassium modified 1:3:8 sodium aluminum phosphate with improved flow characteristics and dust properties particularly suited for refrigerated baking applications.
Crystalline sodium aluminum phosphate was first disclosed in U.S. Pat. No. 2,550,490, and an early baking powder composition incorporating SALP was disclosed in U.S. Pat. No. 2,550,491. Since that time, several modifications of sodium aluminum phosphate have been developed which give different reactivities and performance characteristics.
Sodium aluminum phosphate, also known as SALP, is a well known leavening agent in the baking industry. It finds use in baking powders, self-rising flour mixes, preleavened pancake flours and mixes, prepared biscuit mixes, and prepared cake mixes. It is also used as a melt controlling additive in cheese and as a meat binding agent.
Sodium aluminum phosphate is generally employed in baking applications in a finely divided state due to its substantial insolubility. Furthermore, if relatively large particles of sodium aluminum phosphate are used in bakery applications, they can impart an undesirable, gritty property. However, the use of finely divided sodium aluminum phosphate has several inherent deficiencies, the most serious of which is dusting. Sodium aluminum phosphate dust is very light and rapidly permeates the air in food processing plants, creating cleaning and sanitation problems and unsatisfactory working conditions for the employees. An additional problem in handling sodium aluminum phosphate is that the finely divided particles do not flow easily.
Several proposals have been made in the past for improving the physical handling properties of sodium aluminum phosphate, particularly directed to improving flow characteristics and dust properties. These approaches have generally been directed to agglomerating or pelletizing the SALP as disclosed, for example, in U.S. Pat. No. 3,620,972 which utilizes water as an agglomerating medium. Other methods have involved the employment of various binders such as sugars and crystallizing syrups. Still other approaches utilize the addition of small amounts of colloidal SiO.sub.2 or tricalcium phosphate to the SALP as flow conditioners to improve physical handling properties.
In one particularly relevant approach, U.S. Pat. No. 3,205,073 to Blanch et al. produces a potassium modified sodium aluminum acid phosphate having decreased hygroscopicity. This result is accomplished by modifying the original sodium aluminum phosphate molecule with the introduction of potassium. The potassium is explained as replacing hydrogen atoms in the crystalline lattice of sodium aluminum phosphate. Blanch et al.'s disclosure indicates the "(a)ddition of potassium may be accomplished either during the reaction of the sodium aluminum phosphate, even before the sodium aluminum phosphateforming reaction, or as a final step after preparation." This improved potassium modified sodium aluminum phosphate is described as having hygroscopic properties wherein it does not increase in weight by more than about 20%, preferably not more than about 10% of its original weight during continued exposure at 35.degree. C. and 75% relative humidity for 140 hours.
In example 8 of U.S. Pat. No. 3,205,073, Blanch et al. disclose the preparation of potassium modified sodium aluminum phosphate by reacting potassium hydroxide along with phosphoric acid and soda ash. It is to be noted that Blanch et al. use an 80% H.sub.3 PO.sub.4, and show an Na.sub.2 0 content of 3.53%. The reaction residence time is about 71/2 hours, with the reaction product being cooled over a 4 hour period.
An improvement over U.S. Pat. No. 3,205,073 is U.S. Pat. No. 3,411,872 to Post et al. which attempts to improve the flow characteristics of Blanch et al's potassium modified sodium aluminum phosphate by incorporating the potassium ions in a solvent suspension of an alkanol.
The present invention has achieved an improved SALP product characterized by increased density and reduced dusting properties. Among the advantages accrued thereby, are ease of packaging, use of smaller bags that palletize more easily, decreased hygroscopicity and improved flow characteristics. All of these properties enable better handling, in general, especially under conditions of high humidity.